This invention relates to a locking and alignment mechanism for coupling a shaft into another for the safe off loading of a pallet or other "open type" linear bearing guided device. The coupling to which the invention pertains is of type to fixedly secure the two shafts to each other in alignment, and to allow, quick disassembly of the coupling in order to disconnect the shafts. The coupling of this type is used in applications where disconnection of an otherwise solid shaft train is required.
Typical application of a coupled shaft mechanism like this is on assembly or machining equipment where fixtures or tools must be removed for storage. Typically these fixtures are positioned and held in place with linear bearings mounted to the base of a pallet.
Mechanism prevents the load from coming off the shaft until the second shaft is perfectly joined with primary shaft and locked into place, preventing the load from accidentally falling off equipment or mobile transfer cart.
Shafts must be perfectly aligned for the linear bearing to pass over the connection of one shaft to the other. The mechanism, because the bearing passes over it also, must match in size and be aligned (concentrically) to the primary shafts diameter.
An ideal application, but not limited to, for this mechanism is in the removal of a pallet table on vertical milling machines with pallet changers. These units keep the pallet on linear bearing ways that facilitate the changing of the pallet into the machining center of the mill. Often it is beneficial to replace the pallet with another that is specific to a tooled job. This device allows for a portable pallet change cart to connect to the linear shafts on the machines work surface or pallet staging area, lock the cart shafts to the permanent shafts or the equipment and off load the pallet so it can be moved to storage.
There are many possible ways of connecting shafts, but each have their deficiencies. The typical ways include; a) press fitting; b) set screws, c) using tapered connections; d) use of collets e) bolting shafts together with bracket; f) use of stanchions to prevent the shafts from separating while the load or pallet is being transferred from one shaft to the other; etc.
Sighting the work of Eric Wendling, U.S. Pat. No. 5,304,012 whose coupled shaft design primarily intended for use on drive shafts, is not intended for external shaft alignment, hence preventing a linear bearing from passage over the coupling.
Fred Blumentrath, U.S. Pat. No. 5,333,963 has similar limitations with his shaft coupler.
The inventors in U.S. Pat. No. 4,603,998 successfully demonstrated locking the two shafts together, however, their method also is for internal alignment without consideration of passing a bearing over the coupling.
Other methods of locking two shafts together include threading one shaft into the other or splining one end (as presented in U.S. Pat. No. 5,304,012 and in previously sited U.S. Pat. No. 5,333,963) using a set screw to lock them together. Because the shafts on equipment sited in this application are held vertically by stanchions or posts the shafts can not be rotated for threading or aligning the sprocket teeth. In addition, these other methods work well for their applications, but don't do the dual purpose of preventing the pallet from coming off the shaft when the shafts are not engaged.
Also to be taken into consideration, these methods are both time consuming and difficult to perform when removing pallets off machining centers or assembly apparatus.
To further demonstrate the inferiority of these alternatives, all of the previous art permits the equipment operator to forget to lock the shafts together. In this instance, the shafts could potentially separate during the transfer of the load, resulting in a out of balance weight condition on the cart causing it to topple or droppage of the load where someone might get injured. In the same context, they could leave the mechanical stop out of position, allowing the load or pallet to fall off during transport causing personal injury or damage to property.
This invention requires the equipment operator to lock the shafts together before the load can be removed from the equipment. To disengage the shafts they must unlock the shafts, hence positioning the latch pin in a locked position, as a end of shaft stop, to keep the load or pallet on the appropriate shaft.